1. Field of the Invention
The present invention relates to an adaptive traffic control apparatus and method for controlling connection of arriving calls, utilized in circuit groups of capacity configurable networks such as public telecommunication networks or private telecommunication networks.
2. Description of the Related Art
In public telecommunication networks or in private telecommunication networks, dynamic network reconfiguration in topology and/or bandwidth has been utilized in practice. For example, a transmission path which has been allocated between a pair of switching nodes and used for supporting a circuit-switched network (for example, telephone network, ISDN) may be reallocated to different pair of nodes temporarily to operate the network cost-effectively and adaptively to time-varying traffic demand. A conventional method for reconfiguring networks is a manual operation, in which a target network element, for example, a transmission path between a pair of nodes is put into a maintenance busy state by off-line manual procedure, and then reallocated to another pair of nodes. In the current networks, such a network reconfiguration may be carried out automatically by a software controlled technique implemented in digital cross-connects and switching systems.
Rearrangement within a logical network is also in the category of network reconfiguration. For example, in a circuit-switched network in which calls are served primarily on and on-demand basis, a part of circuit group in the network may be temporarily assigned to call on a reserved basis if the circuit connection for the call has been requested by user and reserved in the network beforehand, and sufficient idle capacity is available for the reserved call at the beginning of the call. This type of network operation may be performed by manual or by software controlled techniques.
In general, in order to reconfigure a network, whether it is physical or logical, it is necessary that the circuit group the network that is targeted to reallocate is entirely idle at the time of reallocation. This means that no calls should remain in progress at the target circuit group at the target time. A conventional method to achieve this requirement is to make the entire circuit group busy prior to the target time so that all the calls in progress may be released before the time, or to execute a forced cut off on the calls in progress.
Making a circuit or circuit group busy for the network operation and maintenance purpose is often referred to as circuit blocking. The circuit blocking is a traffic control technique for rejecting arriving calls to a target circuit or circuit group and releasing calls in progress by the event of call termination for a certain period of time so as to reduce the number of simultaneously connected calls at the scheduled time toward a desired value, for example, to zero. According to the conventional circuit blocking technique, all the calls arriving at the target group from a predetermined initiation time to a target time are rejected without reserve. This time period between the initiation and target time is set with a fixed length which may be predetermined in accordance with statistical nature of calls, the configuration of the target circuit group, and a requested condition on the number of remaining calls at the target time. The longer time period is, the higher the success probability for restricting the number of remaining calls at the target time less than the requested number. In practice, the circuit blocking is initiated sufficiently before the target time by taking account of the target circuit group and the worst case, namely the case where all the circuits are occupied by calls at the beginning of call rejection period.
According to the conventional circuit blocking technique using the call rejection period with a fixed length, however, even if there remain sufficient idle circuits for accepting several new calls at the beginning stage of the call rejection period by chance, all the arriving calls are rejected ignoring such a chance. This will invite unnecessary decrease in circuit utilization.